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Radiation Oncology |
1 From the Department of Radiology (J.S.M., M.L.P.), Radiation Oncology Division (P.A.S.J.), Naval Medical Center San Diego, 34800 Bob Wilson Dr, Suite 14, San Diego, CA 92134-1014; and the Division of Radiation Oncology, University of California, San Diego (P.A.S.J.). Received June 3, 1999; revision requested July 14; revision received September 1; accepted September 15. Address reprint requests to P.A.S.J. (e-mail: pajohnst@nmcsd.med.navy.mil).
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Abstract |
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MATERIALS AND METHODS: Of 133 consecutive patients with prostate carcinoma who were referred to the radiation oncology division between January 1, 1994, and December 31, 1996, 77 underwent definitive radiation therapy that required either contrast-enhanced abdominal and pelvic CT (n = 67) or contrast-enhanced pelvic CT (n = 10). Results of these studies were reviewed and retrospectively categorized.
RESULTS: Forty-eight (62%) of the 77 patients had either negative studies or minor abnormalities that did not require further follow-up. Only two patients (3%) had major abnormalities that required intervention. Five patients (6%) had new findings of clinically important coexistent disease, but no intervention was required.
CONCLUSION: The incidence of clinically important coexistent disease in patients with prostate carcinoma who are referred for definitive radiation therapy is low. Therefore, contrast-enhanced abdominal and pelvic CT in addition to treatment-planning CT is of limited value.
Index terms: Abdomen, CT • Computed tomography (CT), contrast enhancement, 844.12113 • Computed tomography (CT), treatment planning • Cost-effectiveness, 844.30 • Prostate neoplasms, CT, 844.1211, 844.12113, 844.32
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Introduction |
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One prior study (6) addressed the frequency and effect of coexistent disease depicted at screening abdominal and pelvic CT in prostate carcinoma prior to prostatectomy, and screening CT was not found to be cost-effective. To our knowledge, no study has specifically addressed the incidence of coexistent disease in patients opting for definitive radiation therapy. The purpose of this study was to document the frequency of clinically important coexistent disease at contrast material–enhanced abdominal and pelvic CT in patients undergoing definitive therapy for prostate carcinoma and, thus, to determine the number of coexistent disease that might be missed at limited nonenhanced treatment-planning CT. In other words, is limited treatment-planning CT adequate? Or, should patients undergo a more complete examination?
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MATERIALS AND METHODS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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The remainder of the patients who elected definitive radiation therapy underwent either contrast-enhanced abdominal and pelvic CT or contrast-enhanced pelvic CT for treatment planning. A total of 67 patients underwent abdominal and pelvic CT, and 10 underwent only pelvic CT. While this was admittedly a select group, no patient was disqualified from receiving definitive radiation therapy on the basis of discovery of coexistent disease at CT; therefore, no patient was excluded for CT findings of coexistent disease.
All CT examinations except three were performed at the Naval Medical Center San Diego, Calif, by using commercially available scanners (Somatom DRH, Erlangen, Germany; and HiSpeed Advantage, GE Medical Systems, Milwaukee, Wis). All patients received both oral and dynamic intravenous administrations of contrast material. During this period, ionic and nonionic contrast agents from various manufacturers were selectively used according to the American College of Radiology guidelines. All patients received an equivalent intravenous dose of at least 45 grams of iodine. The CT examinations were performed on a clinical basis, and findings were interpreted by the radiology staff (including M.L.P. and J.S.M.) of the Naval Medical Center, all of whom were board certified in diagnostic radiology. The examination results were compiled by means of retrospective chart review.
Radiology reports and medical records were reviewed by a diagnostic radiologist (J.S.M.) for findings of metastatic and coexistent disease, which was defined as any abnormality at CT that was diagnostic or suggestive of disease unrelated to localized prostate carcinoma. Patients were then assigned to categories on the basis of the findings. Some patients had more than one abnormality within a single category but were counted only once within each category. Two patients had multiple findings that fit more than one category; they were assigned to more than one category.
Group A included patients with a negative scan or minor abnormalities that did not require further follow-up. These patients were not included in any other category. Examples of minor abnormalities included hepatic and renal cysts, hiatal hernia, cholelithiasis, and pleural plaques (Figure). Included in this group were patients with low-attenuating foci within the liver and kidneys that were too small to characterize. Also included were patients with CT findings suggestive of the local spread of prostate carcinoma who did not have other abnormalities.
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Group C included patients with findings of clinically important coexistent disease that did not change at follow-up and/or did not require intervention. Group D included patients with a major abnormality that required therapeutic intervention. Group E included patients with clinically important coexistent disease that was previously known or compatible with the known history. Unless stated, no patient had symptoms or clinical findings that were consistent with the coexistent disease discovered at CT.
The median level of prostate-specific antigen was 9.0 ng/mL at the time of presentation, with a range of 0.26–63.65 ng/mL. Median patient age was 70 years at the time of presentation, with an age range of 53 to 80 years and a mean age of 68.56 years. Carcinomas in patients were all clinically staged at the time of initial consultation. Carcinomas in 15 patients (19%) were stage T1, in 51 patients (66%) were stage T2, and in 10 patients (13%) were stage T3. One patient (1%) was categorized as having an unstaged lesion of the prostatic urethra.
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RESULTS |
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Eighteen patients who underwent abdominal and pelvic CT and two patients who underwent only pelvic CT had findings that were categorized to group B. Findings, without complete follow-up, consisted of possible colonic polyp, enlarged azygoesophageal lymph node, mass superior to the bladder, distal esophageal thickening, and single focus of nephrolithiasis. One patient had both an indeterminate hepatic lesion and a 1.5-cm retroperitoneal lymph node. None of these patients developed signs or symptoms related to these findings after at least 2 years of clinical follow-up.
Twelve patients who underwent abdominal and pelvic CT and two patients who underwent pelvic CT had findings of potentially clinically important disease that was later proved at further work-up or follow-up to be benign; these findings did not require intervention or further follow-up. Examples of findings in this group included indeterminate hepatic and adrenal lesions that were later proved to be hemangiomas and adenomas, respectively, at magnetic resonance (MR) imaging. Two patients had findings suggestive of solitary pulmonary nodules, but they had negative findings at follow-up chest CT. Included in this group were six patients with CT findings suggestive of blastic bony metastases who had negative initial and follow-up nuclear medicine bone scans. Two of these patients had additional abnormalities that caused them to be assigned to group B. One had a complex renal cyst that was proved to be a hemorrhagic cyst at ultrasonography (US), and the other had a pelvic mass that was later proved to be a resolved lymphocele or hematoma at follow-up CT.
Five patients (four underwent abdominal and pelvic CT, and one underwent pelvic CT) had findings categorized to group C. Four patients had abdominal aortic aneurysms ranging from 3.0 to 4.5 cm in diameter; one of these was discovered at pelvic CT. One patient was diagnosed with previously unknown cirrhosis and portal venous hypertension.
Only one of the 67 patients who underwent abdominal and pelvic CT and one of the 10 patients who underwent pelvic CT were assigned to group D (major abnormalities requiring therapeutic intervention). One patient had a left renal mass depicted at abdominal and pelvic CT; this patient underwent nephrectomy. Histopathologic examination confirmed renal cell carcinoma. Another patient had an abdominal aortic and right common iliac arterial aneurysm depicted at pelvic CT; the aneurysm was repaired. Both patients had uneventful recoveries and were alive when this article was written.
Four patients had findings of clinically important coexistent disease depicted at abdominal and pelvic CT. These patients were assigned to group E, since these abnormalities were previously known or were compatible with the known history. One patient had a nonfunctioning kidney depicted on a prior intravenous urogram. Another patient had splenomegaly and a history of acute leukemia. Another patient had evidence of a cardiac aneurysm and low cardiac output both of which had been well documented. The final patient had a history of chronic hepatitis and thrombocytopenia related to cirrhosis, with CT findings of cirrhosis and portal venous hypertension.
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DISCUSSION |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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The use of CT in the diagnosis and staging of prostate carcinoma remains somewhat controversial. Study findings have shown the limited utility of abdominal and pelvic CT for staging in patients when the level of prostate-specific antigen is less than or equal to 20 ng/mL (2–4). CT has also been shown to have low utility in the depiction of recurrence and metastatic disease in patients with prostate carcinoma and biochemical failure (10). The use of abdominal and pelvic CT in patients with prostate carcinoma solely for the detection of coexistent disease prior to prostatectomy was shown, in one study (6), not to be cost-effective. In that retrospective review, coexistent disease was defined as clinically important disease that was unrelated to the prostate. This appears to be the only prior study in which the screening of patients with prostate carcinoma at CT for the detection of coexistent disease was specifically investigated.
Patients referred for definitive radiation therapy require at least a limited CT examination for the planning of 3D conformal radiation therapy. The current trend is toward the use of a more limited study that includes only the prostate and adjacent structures. Oral, rectal, and intravenous administration of contrast material may interfere with some treatment-planning algorithms for 3D conformal radiation therapy and should not be used in those instances. A more complete study of the entire abdomen and pelvis, or at least a study of the entire pelvis, with the oral and intravenous administration of contrast material thus requires an examination performed on a separate date. However, this examination would be worth doing only if the detection rate of clinically important coexistent disease was at a reasonable level to warrant the added cost. The purpose of this study was not to determine the cost-effectiveness of such an approach.
The limitation of this study is its retrospective nature. However, the high incidence of prostate carcinoma and the frequent use of radiation therapy to treat it warrant the optimization of care. Clearly, patients will not be well served if severe coexistent disease is frequently missed because of inadequate imaging.
In our study, only two (3%) patients had major abnormal CT findings that required surgical intervention that altered their initial treatment. However, there is no evidence that these findings altered the rate of survival or disease in these patients in any way, since these two patients may have been asymptomatic for many years. Although findings of clinically important coexistent disease were detected in five patients (6%), none of them required a change in medical treatment or surgical intervention. Also, findings that were followed-up showed no change during a 2–4-year period. Therefore, it may be argued that these findings had a limited effect on the mortality and clinical outcome in these patients. Interestingly, 14 patients had false-positive findings at CT that required additional follow-up examination at US, CT, MR imaging, and bone scanning; these examinations added cost and inconvenience, as well as a possible delay in beginning definitive treatment.
There is evidence suggesting that patients with malignant neoplasms referred for radiation therapy, surgery, and chemotherapy have a lower overall incidence of coexistent disease than do age-matched control subjects (11,12). Selection bias is probably involved, since patients with clinically important coexistent disease may be less likely to undergo intensive treatments; this is supported by the fact that patients older than 75 years are less likely to be referred for radiation therapy and surgery than are younger patients (13).
Further, it is likely that patients with prostate carcinoma who are referred for definitive radiation therapy have been previously clinically screened by means of history, physical examination, prior imaging, and laboratory testing. This may, at least partially, explain the low incidence of clinically important coexistent disease seen in our study. Once again, it should be emphasized that no patient was excluded from this study on the basis of CT findings of coexistent disease.
We conclude that the incidence of clinically important coexistent disease detected at screening contrast-enhanced abdominal and pelvic CT in patients with prostate carcinoma who are referred for definitive radiation therapy is low. Therefore, screening with such a protocol in addition to the limited nonenhanced pelvic CT required for the planning of 3D conformal radiation therapy does not warrant the added cost, inconvenience, and small risk.
However, patients who are not candidates for 3D conformal radiation therapy require contrast-enhanced CT imaging of the pelvis for standard planning of radiation therapy. The addition of the abdominal portion of this study may marginally increase the cost, with no added risk or inconvenience. Therefore, in this select minority of patients, the combination of screening and treatment-planning CT may be a consideration. Perhaps a future prospective randomized trial that includes specific figures for cost-effectiveness might further clarify and support our conclusion.
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Footnotes |
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The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government.
Abbreviation: 3D = three-dimensional
Author contributions: Guarantor of integrity of entire study, P.A.S.J.; study concepts, P.A.S.J., J.S.M., M.L.P.; study design, P.A.S.J., J.S.M.; definition of intellectual content, P.A.S.J., J.S.M.; literature research, J.S.M., P.A.S.J.; clinical studies, P.A.S.J., J.S.M.; data acquisition, J.S.M.; data analysis, P.A.S.J., J.S.M., M.L.P.; manuscript preparation, J.S.M., P.A.S.J.; manuscript editing and review, P.A.S.J., J.S.M., M.L.P.
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References |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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This article has been cited by other articles:
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  M. C. Smitt and V. K. Mehta Is Diagnostic Review of Radiotherapy-Planning CT Scans Important in the Conformal Therapy Era? Am. J. Roentgenol., September 1, 2001; 177(3): 521 - 524. [Abstract] [Full Text] [PDF]
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